<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>HTMLDOM</title>
</head>
<body>
     <div id="aa">
         div
     </div>

<script>
    var bb=document.getElementById("aa");
    var cc=bb.innerHTML;
    //div标签中替换一个文本输入框
    //bb.innerHTML="<input type='text'>";
    //div标签中追加一个文本输入框
    bb.innerHTML +="<input type='text'>";



</script>
</body>
</html>